Driving in automotive vehicles is become an increasingly quieter experience. For example, most vehicles utilize sound damping materials and passenger compartment designs to help isolate vehicle occupants from unwanted engine and road noise. Some automotive vehicles include active noise control (ANC) systems designed to cancel or reduce noise levels to help provide a quieter and more peaceful driving experience. In addition to engine sounds and road rumble, other unwanted noises in the vehicle cabin can include wind noise, sounds from other vehicle occupants, and noise generated by the vehicle's heating, ventilation, and air conditioning (HVAC) unit. ANC systems may include one or more microphones within the vehicle cabin detecting cabin noise levels and/or one or more microphones at other locations to pick up other noise sources (e.g., in the engine block).
Some vehicles include a speed-compensated volume (SCV) feature, or speed-sensitive volume control, that automatically adjusts the volume of audio being played through the vehicle's audio or sound system as the vehicle's speed changes, for example, to compensate for road and wind noise as the vehicle accelerates. The speed-volume compensation typically occurs in the background, and the volume adjustment may be achieved by applying a gain to the audio signal in a spectrally varying manner, so that the listener is unaware of the change in volume. The original volume level may be automatically restored once the noise source disappears (e.g., once the car stops accelerating).
Some audio recordings exhibit a wide dynamic range, or a large variation in loudness between notes or phrases. For example, in classical music pieces, certain audio passages within the piece may have a low volume or amplitude (e.g., pianissimo), while other audio passages within the piece have a high volume or amplitude (e.g., fortissimo), even though an overall volume level remains constant during playback of the piece. When playing such audio recordings in a vehicle sound system, the low volume passages may become inaudible due to ambient noise that is louder than that passage, while the high volume passages may become excessively loud, for example, if the volume level had been previously increased to compensate for a pianissimo passage. In such situations, vehicle operators manually adjust the volume up and/or down to compensate for the variation in sound level. For some classical music pieces, volume adjustments are required frequently or in quick succession because the pieces are designed to have fortissimo or forte passages immediately followed by piano or pianissimo passages, and/or vice versa. Such manual volume adjustments can be both bothersome and distracting to the driver.
Accordingly, there is still a need in the art for vehicle sounds systems and methods that can automatically adjust the audio output volume to compensate for ambient noise while also compensating for dynamic sound levels within a given audio recording.